1. Field of the Invention
The present invention relates to a seat structure, more in detail, to a seat structure suitable for transportation machines such as a plane, a train, a ship, a fork lift, and an automobile, or for various chairs used in the inside or the outside of a building.
2. Description of the Related Art
Polyurethane foam or a structure composed of a combination of a polyurethane foam and a metal spring are usually used as a cushioning material used for a seat for a plane, a train, a ship, and an automobile. Among spring characteristics and damping characteristics which polyurethane foam possesses, usually former spring characteristics are thought as important in design in consideration of vibration absorption property and displacement amount.
However, there is an individual difference in a shape of the haunches and a shape of a skeletal structure (shape of the letter S) of the back of a human body, fitness of a seat cushion portion or a seat back portion of a seat is not sufficient for the human body, and there arises deviation in the manner of contact of the human body to the seat cushion portion and the seat back portion of a seat. Therefore, there is a room to improve in point of a body pressure dispersion property. Further, in the above described vehicle seat, it is always required to absorb more efficiently an impact energy caused by collision.
On the other hand, the present inventors have proposed various seat structures for transportation machines in which three-dimensional net member is used as a cushioning material. Especially, a three-dimensional net member shows cushioning characteristic (spring characteristics and damping characteristics) equal to that of polyurethane foam and excellent in air permeability because it can be used as a tension field by providing it as a tension structure member through suspension onto a frame though it is a thin type. When this three-dimensional net member is used as a cushioning material, in order to function the damping characteristics sufficiently due to deformation of the three-dimensional net member, it is provided with almost no tension between the side frames at the time of no load so that the elongation thereof is set to be 5% or less in a static seating state.
However, there is a demand for a seat structure having a narrow seat width, for instance, only about 380 mm to about 400 mm in the seat width. When the three-dimensional net member is provided loosely without almost no rate of elongation on a seat having such a narrow width, since the acromion, the scapula, the haunches and the pelvis come close to the frame of the seat side portion due to thinness of the three dimensional net member, a feeling of something foreign coming from these portions is apt to be felt when a person is seated.
In order to solve the above disadvantage, it is conceivable to make sinking-in small when a person is seated by putting up the three-dimensional net member with predetermined tension. However, when taking this means, a feeling of stroke on seating is disappeared, and hard feeling of seating with no fitness is felt by a seated person and when back-and-forth vibration is inputted, slipping of the backside is apt to occur. Further, there remains a problem in vibration absorption characteristics when a large excitation force such as vibration having a large amplitude is inputted because a spring constant becomes high on seating.
The present invention is achieved in view of the above problems, and the object of the present invention is to provide a seat structure in which rebound of a human body can be suppressed with a small reaction force due to large damping ratio and the impact force inputted into a human body is relaxed by damping the impact force on large deformation such as input of impact force, in particular, by forming a predetermined tension field at least one of a seat cushioning member and a back cushioning member to make a structure in which damping characteristics are thought more important than spring characteristics, and on the other hand, vibration relief property is not lost against input with a small excitation force due to the spring characteristics by making the effect of the damping characteristics small. In addition to this, when a three-dimensional net member is used as a cushioning member, a feeling of something foreign in the frame to a human body is more reduced and a feeling of stroke can be increased in comparison with a seat structure using a conventional three-dimensional net member.
In order to solve the above-described problems, in claim 1 of the present invention, provided is a seat structure comprising a cushion structure having a seat cushioning member for a seat cushion and a back cushioning member for a seat back, wherein the seat cushioning member and the back cushioning member are provided as a tension structure having a tension field formed from an elastic member, and
at least one of the seat cushioning member and back cushioning member is structured to vary the tension in the tangential direction by changing the strain energy in accordance with the magnitude of an excitation force to be an input, and different damping characteristics are exhibited according to the magnitude of the excitation force to be an input in such a manner that the damping characteristics function at a small damping ratio for an input of a small excitation force, and the damping characteristics function at a large damping ratio for an input of a large excitation force.
In claim 2 of the present invention, provided is the seat structure according to claim 1, wherein the cushioning structure forms a vibration system in which an arbitrary portion of the seat cushioning member positioned more front than the vicinity of the boundary of the seat cushion portion and the seat back portion and/or an arbitrary portion of the back cushioning member positioned upper than the vicinity of the boundary portion serves as an free end by putting an extendable direction on the plane surface of the cushioning structure along the back-and-forth direction of the seat cushion portion and along the vertical direction of the seat back portion respectively, and by holding the vicinity of the boundary portion of the seat cushion portion and the seat back portion; and
wherein in at least one of the seat cushioning member and back cushioning member in which the vibration system is formed, tension in the tangential direction is varied by changing the strain energy of the tension structure formed from an elastic member in accordance with the excitation force to be an input, and at least the other of the seat cushioning member and back cushioning member includes a portion exhibiting relatively high spring characteristics in the normal line direction of the tension structure, and has a structure in which an excitation force inputted from the normal line direction to the cushioning member is scatterable into an excitation force in the tangential direction by a combined function of these different characteristics.
In claim 3 of the present invention, provided is the seat structure according to claim 1, wherein any of the seat cushioning member and the back cushioning member which can exhibit damping characteristics different in damping ratio according to the magnitude of the excitation force to be an input is formed of a three-dimensional net member made by connecting a pair of ground knitted fabrics disposed apart from each other with a connecting fiber; and
wherein the cushioning member is put up at a rate of elongation of 30% or less between side frames provided in the seat cushion portion or in the seat back portion at the time of no load, and is arranged to be in a camber shape provided with a top portion bulging upward in the case of the seat cushion portion and forward in the case of the seat back portion within an area of contact with a human body.
In claim 4 of the present invention, provided is the seat structure according to claim 1, wherein both of the seat cushioning member and back cushioning member are formed of a three-dimensional net member which is formed of a pair of ground knitted fabrics disposed apart from each other connected with a connecting fiber; and
wherein any of the cushioning members which can exhibit damping characteristics different in damping ratio according to the magnitude of the excitation force to be an input is put up at a rate of elongation of 30% or less between side frames provided in the seat cushion portion or in the seat back portion at the time of no load, and is arranged to be in a camber shape provided with a top portion bulging upward in the case of the seat cushion portion and forward in the case of the seat back portion within an area of contact with a human body.
In claim 5 of the present invention, provided is the seat structure according to claim 1, wherein any of the seat cushioning member and the back cushioning member which can exhibit damping characteristics different in damping ratio according to the magnitude of the excitation force to be an input is formed of a tension structure with urethane provided with a two-dimensional tension structure and an urethane layer to be layered in the two-dimensional tension structure; and
wherein the cushioning member is put up at a rate of elongation of 30% or less between side frames provided in the seat cushion portion or in the seat back portion at the time of no load, and is arranged to be in a camber shape provided with a top portion bulging upward in the case of the seat cushion portion and forward in the case of the seat back portion within an area of contact with a human body.
In claim 6 of the present invention, provided is the seat structure according to claim 1, wherein both of the seat cushioning member and the back cushioning member are formed of a tension structure with urethane provided with a two-dimensional tension structure and an urethane layer to be layered in the two-dimensional tension structure; and
wherein any of the cushioning members which can exhibit damping characteristics different in damping ratio according to the magnitude of the excitation force to be an input is put up at a rate of elongation of 30% or less between side frames provided in the seat cushion portion or in the seat back portion at the time of no load, and is arranged to be in a camber shape provided with a top portion bulging upward in the case of the seat cushion portion and forward in the case of the seat back portion within an area of contact with a human body.
In claim 7 of the present invention, provided is the seat structure according to any one from claim 3 to claim 6, wherein the top of the bulging portion of the seat cushioning member or back cushioning member having a camber shape is arranged to be deformable to shift each of the positions thereof forward for the seat cushion portion and upward for the seat back portion in a equilibrium state within an area of contact with a human body.
In claim 8 of the present invention, provided is the seat structure according to any one from claim 3 to claim 6, wherein the camber shape of the seat cushioning member or the back cushioning member is formed in a range of 200 mm to 3000 mm in radius.
In claim 9 of the present invention, provided is the seat structure according to any one from claim 3 to claim 6, wherein the seat cushioning member or the back cushioning member having the camber shape is put up between the side frames having an arch shape in the width direction.
In claim 10 of the present invention, provided is the seat structure according to any one from claim 3 to claim 6, wherein the seat cushioning member is formed to be a camber shape, and the top thereof is in front 100 mm or more from the boundary of the seat cushion portion and the seat back portion seen from the side, and in front of the portion under the tuber of ischium.
In claim 11 of the present invention, provided is the seat structure according to any one from claim 3 to claim 6, wherein a rate of elongation of the seat cushioning member or back cushioning member is set to be partially different in the range of the rate of elongation of 30% or less.
In claim 12 of the present invention, provided is the seat structure according to claim 11, wherein the cushioning members are put up at a relatively high rate of elongation compared with other portions in the vicinity of the tuber of ischium and in the vicinity of the lumber vertebra.
In claim 13 of the present invention, provided is the seat structure according to claim 1, wherein any of the seat cushioning member and the back cushioning member which can exhibit damping characteristics different in damping ratio according to the magnitude of the damping force to be an input is made of a layered structure, the layers comprising:
a first soft urethane layer disposed as an upper layer and having an spring constant close to the spring constant of the muscle of a human body;
a second urethane layer disposed as a middle layer and having a high restoring property of 0.1 or more in linearity and 30% or less in hysteresis loss factor;
a third urethane layer disposed as a lower layer and exhibiting the damping characteristics of 0.2 or more in a damping ratio; and
a tension imparting member layered on any of the above-described layers and imparting tension in the tangential direction.
In claim 14 of the present invention, provided is the seat structure according to claim 1, wherein the back cushioning member is designed to have a large deflection amount at the portion corresponding to the position in the vicinity of the scapula, and a small deflection amount at the position corresponding to the position in the vicinity of the acromion and/the lumber vertebra.
In claim 15 of the present invention, provided is the seat structure according to claim 14, wherein the deflection amount of the portion corresponding to the position in the vicinity of the scapula is in the range of 50 to 150 mm.
In claim 16 of the present invention, provided is the seat structure according to claim 14, wherein the spring constant in the vicinity of the equilibrium point of the portion corresponding to the position in the vicinity of the scapula is 15N/mm or less in load characteristic with a compression board of 20 mm in diameter, the spring constant in the vicinity of the equilibrium point of the portion corresponding to the position in the vicinity of the acromion is in the range of 0.2 to 2.0N/mm in load characteristic with a compression board of 50 mm in diameter, and the spring constant in the vicinity of the equilibrium point of the portion corresponding to the position in the vicinity of the lumber vertebra is in the range of 5N/mm or more in load characteristic with a compression board of 20 mm in diameter.
In claim 17 of the present invention, provided is the seat structure according to claim 1, wherein the back cushioning member is formed of a three-dimensional net member, and structured in a manner that frames supporting the three-dimensional net member deform when a large impact vibration or impact force equal to or more than predetermined is applied so that the tension of the three-dimensional net member is lowered.
In claim 18 of the present invention, provided is the seat structure according to claim 1, wherein the back cushioning member is formed with a tension structure with urethane provided with a two-dimensional tension structure and an urethane layer layered on the two-dimensional tension structure, and structured in a manner that frames supporting the tension structure with urethane deform when a large impact vibration or impact force equal to or more than predetermined is applied so that the tension of the tension structure with urethane is lowered.
In the present invention according to claim 1, at least one of the seat cushioning member and a back cushioning member has a structure in which tension along the tangential direction of the cushioning member is changed by difference in a strain energy of the tension structure formed from the elastic member caused in accordance to the magnitude of the excitation force to be an input. Through this structure, different damping characteristics can be exhibited according to the magnitude of the excitation force to be an input. If large damping characteristics function in the case of small excitation force, the inputted excitation force can not be relieved. However, according to the present invention utilizing the characteristics of tension field, since action of the damping characteristics is small for the input of small excitation force, and the spring characteristics of the seat cushioning member or the back cushioning member act relatively large, vibration relief can be possible. Meanwhile, an input vibrational energy having a large excitation force is converted to a strain energy of the tension structure formed from the elastic member and at the same time, tension in the tangential direction of the seat cushioning member or the back cushioning member is declined so that the energy can be scattered and lost by the action of the damping characteristics with relatively large damping ratio.
In the present invention according to claim 2, when small vibration having a small excitation force is inputted, small damping characteristics and relatively large spring characteristics act on one cushioning member out of the cushioning member provided on a seat cushion portion and/or the cushioning member provided on a seat back portion.
More in detail, there are mainly two spring constants on a plane, which are shown due to its tension structure. Among the two spring constants, the one having a softer spring constant, namely the one being easy to be elongated is put up along the back-and-forth direction in the seat cushion portion and along the up-and-down direction in the seat back portion. The boundary portion between the seat cushion portion and the seat back portion is pulled backward and fixed to the frame member. By setting in this way, due to bulging out of the seat cushion and seat back portions, these portions become free ends and the boundary portion is a fixed portion. Thus, a vibration system of an elastic member in which one end is fixed and the other end is free is obtained, so that the present invention can provide a structure which is given a tensile film vibration system, which is different from a conventional structure taking a seat structure as a vibration system having one degree of freedom as a whole. Accordingly, three different spring characteristics act in the up-and-down direction and in the back-and-forth direction in combination, so that the up-and-down vibration is converted to the back-and-forth vibration due to the strain energy of deformation by a plane wave caused by the tension structure of the elastic member. As a result, even if the spring constant in the normal direction with respect to the film is large, its natural frequency is small, so that the resonance range of a human body can be avoided. The excitation force inputted due to the phase difference caused by the interaction of these spring characteristics is damped.
On the other hand, when a large excitation force such as in the case of an impact force is inputted, large damping characteristics can be acted due to the conversion of the tension structure to the strain energy in at least one cushioning member out of these two described above. For instance, in a structure where such a large damping characteristic acts on the seat cushion portion, when a large impact vibration in the up-and-down direction with large deformation is received, a strain energy acting in the tangential direction of the tension structure becomes large owing to the above-described conversion function in the direction of the vibration to lower the tension in the tangential direction and reduce the impact vibration so that rebound of a human body can be suppressed. Further, for the vibration input in the back-and-forth direction, the relational displacement and the acceleration on the seat can be reduced due to restraint of a human body in the seat cushion portion and the seat back portion corresponding to the vicinity of the haunches. Furthermore, by adding the spring characteristics of the seat back portion, the damping ratio is adjusted to make the load dependency small so that the vibration energy is effectively absorbed. Still further, for a large input of the excitation force accompanying a very large displacement in the back-and-forth direction, due to phase difference between the back cushioning member and the seat cushioning member each having different characteristics from each other, displacement occurs in the back slant downward direction of a human body, so that an energy is scattered and lost by high damping characteristics due to the conversion to the strain energy in mainly seat cushion portion.
Similarly, when a structure is made in a manner that large damping characteristics act in the seat back portion, even if a large impact vibration is added in the back-and-forth direction at the collision or the like, rebound forward of a human body can be restrained, and by large damping characteristics, in particular, due to conversion to a strain energy acting on the back of a human body, rebound of a human body can be restrained.
In other words, in the present invention, an integral movement of the seat back and the seat cushion is created by restraining the seat cushion portion and the seat back portion, and the characteristics provided therein are made different from each other, and it is characterized in that a structure is made in which a function of converting the movement direction through phase difference generated by the above-described structure, a vibration damping function to convert a kinetic energy generated by combining different characteristics between the seat cushion portion and the seat back portion into a strain energy in the tangential direction of the tension structure of the elastic member, and vibration characteristics of the film are made available. Through this structure, for instance, when vibration having small amplitude such as vibration in high frequency zone, it can be relieved by the spring characteristics of the cushioning members or lateral vibration of the film, while for vibration with a large amplitude, a force with which a human body was pushed out from each cushioning member by large damping characteristics can be suppressed.
In the present invention according to claim 3 to claim 10, it has a camber-like shape, and since strain energies created by the bulging portion having the camber-like shape are different between the case of small excitation force and that of large excitation force, respective functions described above can be exhibited remarkably.
In the present invention according to claim 11 or claim 12, since two regions composed of a region where function of the spring characteristics is required to be high, and a region where function of the damping characteristics is required to be high can be made up in advance, the above-described respective functions can be exhibited more effectively.
In the present invention according to claim 13, the above-described respective functions can be exhibited by putting urethane materials having different characteristics in tiers in predetermined order.
In the present invention according to claim 14 to claim 16, each function described above can be more remarkably exhibited and at the same time can contribute to further improvement of riding comfort of the car.
In the present invention according to claim 17 or claim 18, when impact vibration or impact force larger than predetermined are received, rebounding of a human body can be further restrained by tension lowering of a human body.